Types of Electrical Wiring in Homes
The wiring in your home is like the veins in your body. Hidden within your walls, the wires transport electricity (which is, in some ways, the blood of the house) to each room so that no matter where you are, you can always turn on the lights. Like your veins, it is important that your electrical wiring be in good health. This protects your house against electrical damage and keeps your family safe. Learning about the types of electrical wiring in homes is a great place to start. Whether you’re building a new home or replacing the wiring in an older home, use this guide to learn more about the types of electrical wiring commonly used in homes these days. We’ve separated the guide into two sections: wires/cables and materiality.
Types of Electrical Wiring: Wires & Cables
Non-Metallic Sheathed Wire
The electrical wiring system in most homes is created with non-metallic sheathed wire (NM). Commonly called Romex, this wire has 2-3 conductors as well as a bare ground wire and it’s coated in plastic. NM is great because it’s quick and easy to install but also relatively inexpensive. It’s available in a variety of sizes and is color-coded by gauge for the electrician’s convenience. You may also see NM-B, with the B representing a heat rating of 194 degrees Fahrenheit, meaning that the cable can operate at high levels without overheating, melting, or causing a fire.
Underground feeder (UF) cables are very similar to NM cables, but they were created for in-ground use and damp-area installation. The wires are embedded in solid thermoplastic for extra protection.
THHN and THWN
If your home is piped, it will also include single strand wires. These insulated wires can be pulled into the same pipe. THHN wire is a common single strand wire. Each letter of THHN wire represents an electric code requirement: T for thermoplastic insulation on the wire, H for heat resistance, another H for high heat resistance (up to 194 degrees Fahrenheit), and N for imperviousness to damage from oil or gas. The THWN wire is similar but instead of an extra H, it comes with a W (for protection against wetness and moisture).
Coaxial cables are used to carry television signals and connect video equipment. They are metallic cables that consist of a central wire conductor and a non-conducting insulator surrounded by mesh or a metal sheath. The coaxial cable is covered in a thin layer of plastic for extra protection.
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Types of Electrical Wiring: Materiality
Years ago (from the late 1960s to the late 1970s), aluminum was a popular choice for residential electrical wiring. However, devices at the time (like outlets, switches, and fans) were not designed to work with aluminum wiring, posing a serious safety hazard. Because of this, aluminum wiring is no longer used in houses. Homes with aluminum wire must have their entire electrical system rewired or undergo “pigtailing,” which entails splicing part of the wire with copper wire.
Copper wire (CU) is currently the go-to choice for home wiring. It is highly ductile, malleable, and electrically conductive, making it a great choice for residential wiring. Plus, it’s easy to install and very strong, so you won’t have to worry about any stretching, breaks, or nicks. Resistant to corrosion and relatively economical, copper wire is a fantastic conductor that will serve your home well for years to come.
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There are a few other types of wires and cables that you may come across in your home (category 5e cables, armored cables, etc.), but they aren’t as common.
With all of these wires and cables, you can find information about the product printed on the sheathing. Important details like the type, gauge, number of wires, grounding, and voltage rating can be found there. You might also see the letters UL, which indicate that the cable has been approved by the Underwriters Laboratories and is safety certified.